This invention relates to a microcooling device for externally supporting electronic components, especially for microelectronic applications, having an internal channel structure through which a coolant can flow, and comprising a base substrate provided with recesses and an external cover layer which covers the recesses in order to form the channel structure. This invention also relates to a method of making a microcooling device comprising creating recesses in a base substrate, and covering the recesses with a sealing cover layer to form a channel structure through which a coolant can flow.
Published German Patent Application No. DE 4,311,839 discloses a microcooling device for cooling electronic components. The microcooling device comprises a base substrate which is structured on one face, and a cover layer disposed on the structured face. To enable electronic components to be disposed on the microcooling device, an insulating layer must be arranged between the electronic components and the material of the microcooling device. As used herein, the term "electronic components" refers to semiconductors, capacitive and inductive elements, resistors, superconductors, circuits made from such components, and the like. A face of the base substrate, which is made of preferably un-doped (i.e. intrinsic) silicon substrate, and which is covered with the covering layer, is provided with recesses which, after the cover layer is sealingly applied, forms on the structured face bearing the recesses a channeled structure through which a preferably liquid coolant flows.
In order to produce the channel structure, the recesses are created, for example by selective etching, in the base substrate which has a flat shape. The recesses are sealingly covered by the cover layer, thereby forming the fluid-carrying channel structure. The cover layer is sealingly bonded to ribs which are composed of the material of the base substrate and which remain standing after the recesses have been created in the base substrate.
Individual electronic components and/or groups of electronic components are disposed, for example by soldering or cementing, on an insulating layer arranged on the microcooling device, so that the waste heat produced by operation of the electronic components is transferred to the coolant through the material of the insulating layer and through the material of the microcooling device. The coolant, which advantageously may be water to which a freezing point lowering substance may optionally be added, absorbs this waste heat and carries it away through the recesses which constitute the channel structure.
Since it is preferred to use un-doped silicon for the base substrate, and since silicon becomes self-conducting beginning at a certain temperature, a microcooling device of this type without any insulating layer is suitable for use only at low temperatures, and even then its suitability is limited. Consequently, it is very desirable to achieve highly efficient cooling of the base substrate. To achieve a large volume flow of coolant and thus realize the best possible cooling effect, the channel structure has relatively large free cross sections. Among other things, these large cross sections are one reason why prior art microcooling devices have had to be made rather large and rather heavy.